Operational amplifiers, more commonly known as "op-amps," are a core component in analog circuit designs and analog integrated circuits ("ICs"). An ideal operational amplifier is a differential input, single-ended or differential-ended output amplifier having infinite gain, infinite input impedance, and zero output impedance, and infinite bandwidth. Thus, the operational amplifier is well suited for a variety of applications in integrated circuits including filters, oscillators, converters, regulators, signal processors, and control circuits, just to mention a few.
Real operational amplifiers don't exhibit the idealized characteristics and performance of the ideal op-amp. In particular, real op-amps don't have infinite gain; don't have infinite input impedance; don't have zero output impedance; and, don't have infinite bandwidth.
Accordingly, there is a need in the art for an op-amp that has high input impedance, low input current, sufficient gain-bandwidth product and open loop gain, and can be easily fabricated with an integrated circuit process. Furthermore, to minimize expensive external components and connections, it is desirable that such an op-amp should not require external or discrete parts to achieve these characteristics.